Method and device for setting connecting elements that are self-drilling without chip formation

ABSTRACT

The invention relates to a method for setting connecting elements ( 16 ), such as screws or blind rivets, which are self-drilling without chip formation, in one or more plates, wherein the plate(s) are heated by electrical energy shortly before the start of the setting process, wherein the heating is accomplished by means of an induction coil ( 26 ), which is arranged near a point on the plate(s) at which the connecting element ( 16 ) is set. The invention further relates to a device ( 10 ) for setting a connecting element ( 16 ), which is self-drilling without chip formation, in one or more plates, comprising an induction coil ( 26 ), which at least before and/or during the setting process is arranged near a point on the plate(s), at which the connecting element ( 16 ) is set.

TECHNICAL FIELD

The present invention relates to a method for inserting connectingelements which are self-boring without chip formation, such as screws orblind rivets, into one or more metal sheets, the metal sheet(s) beingheated by means of electrical energy shortly before commencement of theinsertion operation. In addition, the present invention relates to acorresponding device for inserting a connecting element which isself-boring without chip formation into one or more metal sheets.

Connecting elements which are self-boring without chip formation, whichare also referred to as flow-hole drilling screws or flow-holeconnecting elements, are increasingly used as the preferred choice inindustry, since rough-drilling and thread-cutting can be avoided whenthey are used and no chips occur when they are handled.

PRIOR ART

However, until now, these connecting elements could only be used inconjunction with normal steel sheets and aluminium sheets. Use inhigh-tensile steel sheets without rough-drilling ceased, since thethermal energy which can be transmitted by the connecting element is notsufficient to appropriately soften a high-tensile steel sheet.

As a solution to this problem, the closest prior art in this regard, DE196 34 417 A1, has already proposed heating the material of the metalsheet into which the connecting element is to be inserted by means ofelectrical energy in the form of an electric arc between a tool used forboring and the metal sheet.

This proposal, however, has considerable drawbacks, since the currentdensity is always substantially higher in the auger bit of the boringtool than in the large-area metal sheet. As a result, the auger bitheats up more than the metal sheet and is softened more than the metalsheet, which is clearly counter-productive from the perspective of theobject addressed herein. In addition, the bit of the boring tool, theform of which bit is of exceptionally great significance to correctboring, is damaged or deformed by the electric arc and the associatedburning of the contacts, and this in turn can render boring considerablymore difficult.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to make it possibleto insert connecting elements which are self-boring without chipformation into high-tensile steel sheets directly during heating of themetal sheet and without using a separate boring tool.

According to the invention, this object is achieved by a method in whichheating takes place by means of an induction coil which is arranged inthe vicinity of a point on the metal sheet(s) at which the connectingelement is inserted.

Similarly, the present object can be achieved according to the inventionby a device for inserting a connecting element which is self-boringwithout chip formation into one or more metal sheets, which device isprovided with an induction coil which is arranged, at least beforeand/or during the insertion operation, in the vicinity of the point onthe metal sheet(s) at which the connecting element is intended to beinserted.

It is preferable in this case for the induction coil to beconcentrically arranged with respect to the point on the metal sheet(s)at which the connecting element is intended to be inserted.

It is particularly preferable for the induction coil to have a centralopening and to remain above the metal sheet(s) during the insertionoperation, and for the connecting element to be inserted through thiscentral opening in the induction coil.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention is described in greater detailon the basis of the embodiment depicted in the appended drawings, inwhich:

FIG. 1 is a front view of a device according to the invention forinserting connecting elements which are self-boring without chipformation;

FIG. 2 is a side view of the device in FIG. 1;

FIG. 3 shows detail A in FIG. 1; and

FIG. 4 shows detail B in FIG. 1.

PREFERRED MEANS OF CARRYING OUT THE INVENTION

FIG. 1 shows a device according to the invention for inserting aconnecting element which is self-boring without chip formation into oneor more metal sheets. The device 10 in this case comprises a retainer 12which bears, in the manner of an upright drill, a screwdriver 14. At itsscrewing tool, the screwdriver bears a connecting element 16, which inthis case is a screw which is self-boring without chip formation, thatis, a connecting element 16 having a self-boring auger bit and outerthread.

In the present embodiment, the connecting element 16 is intended to beinserted into two metal sheets 18, 20 which are arranged on a support 22having a recess 24 beneath the point at which the connecting element 16is intended to be inserted.

According to the invention, a circular ring-shaped induction coil 26 isarranged above the recess 24 and above the two metal sheets 18, 20. Theinduction coil 26 in this case has a central opening which isconcentrically arranged with respect to the point at which theconnection element 16 is intended to be inserted.

According to the invention, the insertion operation then proceeds asfollows.

The induction coil 26 is supplied with an alternating current ofsuitable frequency and voltage for a sufficiently long period of timefor the region of the metal sheets 18, 20 which is beneath the inductioncoil 26 and thus above the recess 24 to be sufficiently heated.

Thereafter, the connecting element 16 which is self-boring without chipformation is inserted, in the manner in which connecting elements whichare self-boring without chip formation known in the prior art areinserted, at the point in the two metal sheets 18, 20 which has now beenheated according to the invention.

The recess 24 on one hand provides the space which accommodates theportion of the connecting element 16 which projects downwardly out ofand beyond the metal sheets 18, 20 after insertion, and on the otherhand prevents the metal sheets 18, 20 from cooling or prevents thermaldissipation therefrom via the support 22.

According to the invention, even metal sheets 18, 20 made ofsubstantially harder steel categories are able to be connected to orfitted with connecting elements which are self-boring without chipformation.

As an alternative to the embodiment explained here for inserting theconnecting element 16 into two metal sheets 18, 20, the connectionelement is also able to be inserted according to the invention into justa single metal sheet, or into three or more metal sheets.

1. Method for inserting connecting elements (16) which are self-boringwithout chip formation, such as screws or blind rivets, into one or moremetal sheets (18, 20), said method including the steps of: heating themetal sheet(s) (18, 20) by means of electrical energy shortly beforecommencement of the insertion operation, heating takes place by means ofan induction coil (26) arranged in the vicinity of a point on the metalsheet(s) (18, 20) at which the connecting element is inserted (16). 2.The method according to claim 1, wherein the induction coil (26) isconcentrically arranged with respect to the point on the metal sheet(s)(18, 20) at which the connecting element (16) is inserted.
 3. The methodaccording to claim 2, wherein the induction coil (26) has a centralopening and remains above the metal sheet(s) (18, 20) during theinsertion operation, and the connecting element (16) is inserted throughthe central opening in the induction coil (26).
 4. Device (10) forinserting a connecting element (16) which is self-boring without chipformation into one or more metal sheets (18, 20), said devicecomprising: an induction coil (26) arranged, at least before and/orduring the insertion operation, in a vicinity of a point on the metalsheet(s) (18, 20) at which the connecting element (16) is inserted. 5.The device (10) according to claim 4, wherein the induction coil (26)is, at least before and/or during the insertion operation,concentrically arranged with respect to the point on the metal sheet(s)(18, 20) at which the connecting element (16) is inserted.
 6. The device(10) according to claim 5, wherein the induction coil (26) has a centralopening and is arranged such that the connection element (16) penetratesthis opening during the insertion operation.